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--- Small-step SOS: Adding print to IMP ---
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Suggested steps to follow in order to extend the oringinal small-step SOS
of IMP in Maude to include a print statement:

1) Modify imp-smallstep.maude: Include output.maude at the begining, and 
   add Maude commands for executing sumPrintPgm at the end.

2) Run imp-smallstep.maude: Everything working before should still work;
   sumPrintPgm gets stuck when the first print statement is encountered.

3) Modify imp-semantics-smallstep.maude:
   a) Include module OUTPUT in module IMP-CONFIGURATIONS-SMALLSTEP.
   b) Add a new output component to the statement configurations.
   c) Modify the existing smallstep SOS rules using the old statement
      configurations (i.e., the rules of all statements) to work with
	  the new staments configurations that also include an output.
   d) Change the rule for variable declarations to include the empty output
      in the initial configuration.

4) Modify imp-smallstep.maude: Add the output buffer component
   (holding an empty buffer) to any configuration holding an explicit state
   that appears in any of the concrete rewrite or search commands.

5) Run imp-smallstep.maude: Everything working before should still work, and
   should include and empty output buffer in the result configurations;
   sumPrintPgm still gets stuck when the first print statement is encountered.

6) Add the actual small-step SOS of print, which consists of two rules.

7) Run imp-smallstep.maude and check that all programs evaluate properly.


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--- Observations, thoughts ---
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1) Statement configuration had to change in order to hold the output.

2) Consequently, all rules corresponding to statements had to change, too.

3) We also had to change the rule for programs, to initiate the empty output buffer.
